A variety of situations require hydrophilic articles. One example is within the fuel cell art. Many fuel cell arrangements include water transport plates for controlling water, air and fuel flow within a fuel cell assembly in a known manner. Traditionally, water transport plates have included porous, hydrophilic flow fields that include flow channels for directing fluid in a desired manner. Many such flow fields comprise graphite, a resin and a wettability component. For example, it is known to treat porous graphite plates with a metal oxide post-treatment to impart wettability to the plate. It is also known to add a metal oxide as one of the components for making a water transport plate. Another example includes adding hydrophilic carbon black. In many of those instances, the wettability component is added as a separate component in a mixture containing resin such that the resin binds the wettability component in place. There is no effect on the graphite, itself, using the traditional approach.
U.S. Pat. No. 5,942,347 shows one example technique where a porous bi-polar separator plate has at least one electronically conductive material, at least one resin and at least one hydrophilic agent. Each of these components is substantially uniformly distributed throughout the separator plate of that document. The hydrophilic agent in that document is selected from material such as oxides of Ti, Al, Si and mixtures of them. There are at least two difficulties with this approach. First, it is very difficult to uniformly distribute materials as suggested in that patent. Secondly, because the oxides are dielectric, using hydrophilic or wetting agents of the type described there can increase the electrical resistance of such a separator plate, which is undesirable. Therefore, it is difficult to achieve uniform distribution as suggested in that document without increasing electrical resistance.
Such wettability treatments or additives have been required because the graphite is generally hydrophobic. Without the wettability agent or treatment, traditional graphite based water transport plates are hydrophobic and not suitable for their intended use. Graphite particles comprise carbon atoms arranged in a manner that typically provides a relatively low surface energy such that the graphite particles are essentially hydrophobic. Carbon atoms within a graphite crystal are arranged in a plurality of generally parallel planes. The bonds between the carbon atoms within the planes are very strong. Graphite particle surfaces that are aligned with such planes (i.e., basal plane surfaces) have a relatively low surface energy.
It is desirable to provide an improved process for making hydrophilic articles such as water transport plates. For example, it would be useful to make the fabrication process less complicated and to reduce costs by taking a different approach that does not include the traditional wettability additives or wettability enhancing agents. This invention addresses that need.